1. Field of the Invention
The present application relates to a semiconductor laser diode (LD), in particular, to an LD with a shortened cavity length.
2. Related Background Arts
An optical communication usually implements an LD as an optical signal source. As the capacity of the optical communication system drastically increases, the optical source is requested to modulate signals faster as long as possible. Recent communication systems request the modulation speed exceeding 15 GHz, sometimes reaching 30 GHz. For such high speed modulations, conventional LDs with the edge-emitting type have been requested to shorten the cavity length thereof, because, the high speed operation of an LD very strongly depends on the cavity length. However, because of the productivity of au LD, the cavity length thereof is restricted to a few hundreds of micron-meters. The present application is to provide one solution for such an LD with shortened cavity length.